1. Field of the Invention
The present invention is directed to esophageal stethoscopes, and specifically to an esophageal stethoscope including a microphone element at its distal end for detecting heart and respiratory sounds produced by a patient when the stethoscope is inserted into the patient's esophagus.
2. Description of the Prior Art
Conventional esophageal stethoscopes include a length of plastic tubing one end of which, the distal end, may have a number of openings formed through the tube wall and a relatively thin protective covering sealed over the openings to prevent body fluids from entering the tube when the distal end is inserted into a patient's esophagus. The other end of the tube, i.e., the proximal end, may be connected to a fitting such as a "Luer" type of fitting for connecting with a set of stethoscope earpieces.
Esophageal stethoscopes are often used by anesthesiologists who listen to the heart and respiratory sounds of a patient during the course of a surgical procedure. The anesthesiologist listens for changes in the heart or respiratory sounds which serve to indicate the existence of a problem requiring the immediate attention of the anesthesiologist. In the event the anesthesiologist must be located a considerable distance from the patient during a surgical or other operating procedure, it will be understood that the length of the stethoscope tubing must be correspondingly increased in order that it remain connected with the stethoscope earpieces which must always be worn by the anesthesiologist. However, as the length of the tubing is increased, the intensity of the sounds reaching the proximal end of the tubing diminishes accordingly. Further, there are instances when the anesthesiologist must move about the operating room to attend to required tasks. This requires that the tubing be temporarily disconnected from the stethoscope earpieces, so that the patient's heart and respiratory sounds are not monitored during such times. This presents a potential hazard for the patient.
It is also known to provide a microphone at one end of a length of flexible tubing so as to convert heart sounds picked up by a chest piece at the other end of the tubing into electrical impulses. For example, U.S. Pat. No. 2,699,465 issued Jan. 11, 1955, to S. Hamilton shows such an arrangement which is used in a warning system for indicating the cessation of cardiac funtions. Another device is also known in which the proximal end of an esophageal stethoscope is provided with a Luer fitting for coupling with a microphone of an FM transmitter, thereby allowing sounds conveyed to the proximal end of the tubing to be monitored by a receiver at a location remote from the operating table.
It will be appreciated, however, that the placement of a microphone at the proximal end of a stethoscope tube will result in the detection and reproduction of sounds developed over the entire length of the tube which sounds may not be among those desired to be heard. For example, bending movement of the stethoscope tube will produce noises at the proximal end of the tube and, since the microphone is unable to discriminate between these noises and the respiratory and heart sounds originating from the distal end of the tube, these noises will be converted into electrical signals thus making the monitoring of the heart and breathing sounds more difficult.